In any optical system, for example a microscope or an optical measurement or inspection system, there exists a plurality of components that are adjustable or alignable in particular for the purpose of light beam guidance. Such components are optical and mechanical elements such as, for example, individual lens elements, lens groups, prisms, mirrors, optical filters, light guides, lamps, or slits, diaphragms, objective turrets, camera mounts, or microscope stages. All the components must be aligned with one another to ensure an appropriate beam path and thus also an appropriate optical performance of the optical system. An alignment of the components prior to initial operation of the optical system, which must be performed very precisely depending on the components, is therefore normally necessary. A realignment may also be necessary during operation, however, after certain operating periods.
The alignment is generally performed by manual operation directly on the components to be aligned. The components are mounted so as to be mechanically displaceable and/or rotatable with respect to their mounts. In the simplest case, longitudinal displacement or rotational movement of the components can be accomplished by sliding, using linear or curved elongated holes. For stringent requirements, correspondingly precise guide rails, rotary apparatuses, or precise ball bearings are used. Mechanical tools, which in some cases are manufactured especially for the alignment of specific subassemblies, are placed directly onto the components and the latter are adjusted in terms of their spatial position and/or rotational position.
In the case where a microscope constitutes the optical system, the alignment can be accomplished during assembly on the other hand by means of simple visual checks of the components. In most cases, however, the alignment is performed on the microscope under operating conditions. A specimen is continuously observed under the microscope by looking into the microscope's eyepiece. Or the specimen is imaged by an electronic camera mounted on the microscope, and its image is observed online on a monitor. At the same time, the relevant components are manually set with alignment tools.
The fact that access to the components is often limited, however, makes the alignment operation cumbersome and inconvenient. Alignment is especially troublesome if the individual components are located physically far away from one another, for example because it is impossible to look into the microscope tube or because the monitor must be appropriately rotated in each case so it can be observed during the alignment setting process. This procedure is also time-consuming.
Similar considerations also apply to the adjustment of components for other purposes that do not serve for alignment but rather can be used to modify parameters of the microscope during operation. Depending on the microscope mode or the requirement resulting from the observation or measurement task, the optical elements or mechanical subassemblies must be mechanically adjusted in order to be optimally arranged for the respective microscope mode. For example, the position of diaphragms, filters, or mirrors in the beam path must be modified; the offset lens system of an autofocus system must be adjusted for purposes of selecting the focal plane; or the width of slits or the orientation of the illumination system must be modified in order to achieve optimization of the microscope or the measurement or inspection system for a specific task. If these adjustments are not automated, the user must make the adjustments him- or herself directly on the subassemblies. In this case as well, the overall configuration of the microscope means that not all subassemblies are equally easily accessible, and the settings cannot always be carried out ergonomically.
In the case of larger mechanical or optical assemblages in particular, for example measurement and inspection devices for the semiconductor industry for the examination of wafers, mechanical and optical subassemblies are often located far away from one another and are difficult to reach for adjustment during operation or for alignment. Measurement and inspection devices of this kind contain not only optical subassemblies but also a plurality of purely mechanical subassemblies, such as an input station for cassettes that are loaded with wafers or masks that are to be examined, and apparatuses for removing the individual wafers or masks from the cassettes and transporting them to the microscope stage. For precise operation, the mechanical alignment of these mechanical handling systems, and also of any electronic or optoelectronics monitoring elements, must be correspondingly good. In this context, access to the components that are to be aligned or adjusted, and their operability for controlled adjustment, is particularly difficult because of the large overall configuration of the devices.